Energizing system for color purity apparatus



Aug. 20, 1968 LEMKE ET AL 3,398,319

ENERGIZING SYSTEM FOR COLOR PURITY APPARATUS Filed Dec. 14, 1965INVENTOR. A E/65v! ZFMKE M! M war/I 3 United States Patent 3,398,319ENERGIZING SYSTEM FOR COLOR PURITY APPARATUS Eugene Lemke and Neal W.Hursh, Indianapolis, Ind.,

assignors to Radio Corporation of America, a corporation of DelawareFiled Dec. 14, 1965, Ser. No. 513,693 4 Claims. (Cl. 315-27) ABSTRACT OFTHE DISCLOSURE An auxiliary yoke having horizontal and vertical coils iscontrolled by apparatus including a saturable reactor having an A.C.winding and a -D.C. winding. The horizontal coils of the auxiliary yokeare coupled to the horizontal deflection Wave source through the A.C.reactor winding. As the temperature changes, the current in the DC.winding is changed, causing the inductive reactance of the A.C. windingto change, thereby affecting the energization of the horizontalauxiliary deflection coils and the effective horizontal deflectioncenter as a function of the temperature change and the horizontaldeflection angle. The energization of the vertical coils of theauxiliary deflection yoke, and thereby the vertical deflection center,is changed as a function of the vertical deflection angle and by theoperation of magnetic contacts responsive to the current in the reactorD.C. winding.

This invention relates to cathode ray tube deflection systems andparticularly to apparatus by which to control wide angle beam deflectionin television picture tubes such as, for example, shadow mask type colorpicture tubes.

In order to achieve wide angle beam deflection with good color purity inshadow mask color television picture tubes, it is necessary not only tomaintain accurate coincidence of the eflective horizontal and verticaldeflection centers but also to insure that the effective deflectioncenters are proper under all conditions to direct the electron beamsthrough the appropriate apertures in the shadow mask to strike thedesired phosphor elements. The beam deflection apparatus in such acathode ray tube must effect not only the wide angle deflection of thebeams to scan a raster at the luminescent screen, but also must functionwith a minimum of coma, astigmatism, degrouping and other undesiredelectron-optical effects. When the deflection angle becomes relativelygreat, such as 90 or more, it is difficult to design a single yoke bywhich to achieve all of the desired results. These problems become moresevere when the neck of the cathode ray tube is decreased in. diameter,which is in conformity with present trends, because one or more of thebeams tends to strike the neck of the tube and, consequently, will notreach the luminescent screen.

Another problem encountered with wide angle beam deflection systems isthat resulting from structural deformations occurring within the picturetube itself under varying temperature conditions. For example, theshadow mask in a color television picture tube may become distortedrelative to the phosphor screen at elevated temperatures. It isdesirable that some modification of one or both of the eflFective beamdeflection centers be made as some function of the temperatures withinthe tube. Such deflection center modification is particularly desirablein rectangular tubes because of the tendency of a rectangularly shapedshadow mask to become unsymmetrically distorted at elevatedtemperatures. Distortions of the character described, detract from colorpurity in such picture tubes.

It, therefore, is an object of the present invention to provide a beamdeflection system by which to modify the ice eflective horizontal and/orvertical deflection centers of a cathode ray picture tube as functionsof both the angle of beam deflection and of the environmentaltemperature.

In accordance with this invention, there is provided a deflection systemtor a cathode ray picture tube which includes a main deflection yokewhich is energizable from suitable deflection wave sources to deflectone or more electron beams suitably to scan a substantially rectangularraster at a target electrode. The system also includes an auxiliarydeflection yoke which is operable suitably to modify the effectivedeflection center of the main yoke. The control apparatus for operatingthe auxiliary yoke includes a variable reactor which has a main windingand a control winding. The impedance of the main winding and thereby theenergization of the auxiliary yoke at the horizontal beam deflectionrate are changed by a change in the energization of the control winding.The energizing circuit for the control winding includes an element(e.g., a thermistor) whose impedance changes in response to itsenvironmental temperature. The auxiliary yoke control apparatus alsoincludes a temperature responsive switch (e.g. of the magnetic tape)having contacts which, under certain temperature conditions, enablesenergization of the auxiliary yoke at the vertical beam deflection rateby current derived directly from the vertical deflection wave sourceand, under other temperature conditions, elfectively energizes theauxiliary yoke at the vertical deflection rate by current induced fromthe main deflection yoke.

For a better understanding of the invention, reference now is made tothe following description which is taken in conjunction with theaccompanying drawing.

The single figure of the drawing is a schematic circuit diagram of aportion of a television receiver embodying the color purity apparatus ofthe invention.

In the drawing, a shadow mask type of color television picture tube 1 isprovided with a main deflection yoke 2 and an auxiliary deflection yoke3. The picture tube may be a 25 inch RCA type 25AP22 which has asubstantially rectangular screen and is one in which the three electronbeams are deflected by means including the yoke 2 through angles up toapproximately It will be understood, however, that the invention mayalso be used with other types of picture tubes such as, for example, a21 inch RCA type 21FBP22A which has a round screen and is one in whichthe electron beams are deflected through angles up to approximately 70.The main deflection yoke 2 may be of the 90 variety such as disclosed inPatent 3,169,207 granted Feb. 9, 1965, to M. J. Obert and R. L. Barbin,when a picture tube of the 25 inch rectangular variety is used. The yoke2 alternatively may be of the type disclosed in Patent 2,824,267 grantedFeb. 18, 1958, to W. H. Barkow, when a picture tube of the 70 roundvariety is used. It is to be understood that the present invention isnot limited to use with such tubes as those referred to, but also may beused with substantially equal facility with other types of tubes such asa 19 inch rectangular tube identified by RCA type 19EYP22. The maindeflection yoke 2 has a pair of horizontal deflection coils 4 and a pairof vertical deflection coils 5.

The auxiliary deflection yoke 3 also has a pair of horizontal deflectioncoils 6 and a pair of vertical deflection coils 7. The auxiliary yokemay take any of the forms shown in the concurrently filed application ofR. L. Barbin, Ser. No. 513,774 and titled Auxiliary Beam DeflectionYoke. The auxiliary yoke may be mounted in front of the main deflectionyoke 2 as shown in the drawing or alternatively behind the main yoke asdesired.

The beam deflection circuit includes horizontal and vertical outputtubes 8 and 9 which, it will be understood, are suitably driven in aconventional manner by substantially sawtooth voltage waves respectivelyat the line and field repetition rates. The output circuit of thehorizontal output tube is connected to a winding 11 of a horizontaloutput transformer 12. The horizontal deflection coils 4 of the maindeflection yoke 2 are connected to the transformer winding 11 in aconventional manner.

The vertical output tube 9 is connected to the primary winding 13 of avertical output transformer 14, the secondary winding 15 of which isconnected to the vertical deflection coils of the main deflection yoke 2in series with the vertical deflection coils 7 of the auxiliary yoke 33.

The horizontal deflection coils 6 of the auxiliary yoke 3 are connectedthrough a two-part or alternating current winding 16 of a saturablereactor 17 to an auxiliary winding 18 of the transformer 12. Thepulsating voltage produced in the winding 18 effects a substantiallysawtooth current flow at the line repetition rate through the horizontaldeflection coils 6 of the auxiliary yoke 3. The amplitude of thissawtooth current depends on the inductive impedance of the alternatingcurrent winding 16 of the reactor 17. The impedance of the winding 16 isvariable as a function of the energization of a control or directcurrent winding 19 of the reactor 17. The winding 19 is energized from asource of direct current such as represented by a battery 21 by means ofa circuit which includes a thermistor 22. The thermistor is mounted in apart of the chassis which experiences temperature variations comparableto and/or representative of the temperature changes to which the shadowmask and associated parts of the picture tube 1 are expo ed. As anexample, the thermistor may be mounted on the core of the horizontaloutput transformer 12. Although not necessarily limited thereto, thethermistor 22 has a negative temperature coefiicient whereby itsresistance decreases with heat.

A reed switch 23 is mounted inside of the control winding 19 of thereactor 17. The switch may be of the type described in an article titledMagnetic Reed Switches and Relays by Gary A. Lehmann, published inElectronics World of September 1965 at pages 23 to 26 and 64. The switch23 has two normally closed magnetic contacts 24 which are connectedrespectively to opposite ends of the vertical deflection coils 7 of theauxiliary yoke 3. A switch with normally open contacts may also be usedwith a slightly modified auxiliary yoke of the type disclosed in theconcurrently filed Barbin application.

In the operation of the apparatus embodying the invention, when thetelevision receiver is first turned on, the thermistor 22 is relativelycool and its resistance is sufficiently high that only a small currentflows through the direct current winding 19 of the reactor 17. As aresult, the inductive impedance of the alternating winding 16 of thereactor 17 is relatively high so that the horizontal deflection coils 6of the axuiliary yoke 3 are energized from the output transformerwinding 18 only to a small degree. The magnetic field produced by thedescribed small current flow in the reactor winding 19 is insufficientto open the reed switch contacts 24. Hence, the vertical deflectioncoils 7 of the auxiliary yoke 3 are energized by induction from thevertical deflection coils 5 of the main yoke 2. Thus, at normaltemperatures the described operating control of the coils 6 and 7 of theauxiliary yoke 3, together with the usual energization of the coils 4and 5 of the main yoke 2, produce a given effective deflection centerfor the electron beams.

As the temperature increases, the resistance of the thermistor 22decreases permitting more current to flow through the direct currentwinding 19 of the reactor 17. As a result, the inductive impedance ofthe alternating current winding 16 decreases and the energization of thehorizontal deflection coils 6 of the auxiliary yoke 3 increases. Theeffective electron beam deflection center is, thus, suitably modified tomaintain the desired relationship between the electron beams and theshadow mask.

The described inductive energization of the vertical deflection coils 7of the auxiliary yoke is not changed until a particular elevatedtemperature is reached. At such time the direct current energization ofthe reactor winding 19 is enough to produce a magnetic field ofsuflicient strength to open the reed switch contacts 24. This actioneffectively enables energization of the vertical deflection coils 7 ofthe auxiliary yoke 3 from the vertical deflection output transformerwinding 15. Thus, there is produced a suitable modification of theeffective vertical beam deflection center.

It will be noted that the modification of the effective beam deflectioncenters is gradual and continuous horizontally and sharp and abruptvertically. This has been found to be quite satisfactory because themodification of the effective vertical deflection center is lesscritical than that of the horizontal deflection center owing to thesmaller vertical deflection angle.

The apparatus shown and described constitutes a practical beamdeflection system which operates to modify the effective deflectioncenter of a cathode ray picture tube as functions of the angle of beamdeflection and of the environmental temperature.

What is claimed is:

1. In a deflection system for a cathode ray picture tube and including amain deflection yoke having horizontal and vertical coils energiz-ablerespectively from horizontal and vertical deflection wave sources todeflect an electron beam horizontally and vertically to scan asubstantially rectangular raster at a luminescent screen and alsoincluding an auxiliary deflection yoke having horizontal and verticalcoils energiz-able to modify the effective deflection center of saidmain yoke, apparatus for energizing said auxiliary yoke comprising:

a saturable reactor having an alternating current winding and a directcurrent Winding;

means including said alternating winding connecting the horizontal coilsof said auxiliary yoke to said horizontal deflection wave source in amanner to control the energization of said horizontal auxiliary yokecoils and hence the modification of the effective horizontal deflectioncenter as a function of the inductive impedance of said alternatingcurrent winding and as a function of the horizontal deflection angle ofsaid beam;

means to vary the energization of said direct current reactor windingand hence the inductive impedance of said alternating curent reactorwinding as a function of temperature;

means operative at certain temperatures to vary the energization of saidvertical auxiliary yoke coil in a manner to modify the effectivevertical deflection center in one sense as a function of the verticaldeflection angle of said beam; and

means including a set of magnetic contacts at other temperaturesoperative in response to current in said direct current winding-to varythe energization of said vertical auxiliary yoke coils in a manner tomodify the effective vertical deflection center in an opposite sense tosaid one sense as a function of the vertical deflection angle of saidbeam.

2. In a deflection system for a cathode ray picture tube and including amain deflection yoke having horizontal and vertical coils energizablerespectively from horizontal and vertical deflection wave sources todeflect an electron beam horizontally and vertically .to scan asubstantially rectangular raster at a luminescent screen and alsoincluding an auxiliary deflection yoke having horizontal and verticalcoils energizable to modify the effective deflection center of said mainyoke, apparatus for energizing said auxiliary yoke comprising:

a saturable reactor having an alternating current Winding and a directcurrent winding;

means connecting said alternating current winding in circuit with thehorizontal coils of said auxiliary yoke and said horizontal deflectionwave source in a manner to control the energization of said horizontalauxiliary yoke coils and hence the modification of the effectivehorizontal deflection center as a function of the inductive impedance ofsaid alternating current winding and as a function of the horizontaldeflection angle of said beam;

means responsive to temperature changes and connected in circuit withsaid direct current reactor winding and a source of direct current in amanner to vary the energization of said direct current winding and hencethe inductive impedance of said alternating current reactor winding as afunction of temperature;

means operative at first temperatures connecting the vertical coils ofsaid auxiliary yoke to said vertical deflection :wave source, whereby tovary the energization of said vertical auxiliary yoke coils in a mannerto modify the effective vertical deflection center in one sense as afunction of the vertical deflection angle of said beam; and

means including a pair of magnetic contacts located adjacent to saiddirect current reactor Winding and operative at other temperatures inresponse to current in said direct current winding to vary theenergization of said vertical auxiliary yoke coils in a manner to modifythe effective vertical deflection center in an opposite sense to saidone sense as a function of the vertical deflection angle of said beam.

3. In a deflection system for a cathode ray picture tube and including amain deflection yoke having horizontal and vertical coils energizablerespectively from horizontal and vertical deflection wave sources todeflect an electron beam horizontally and vertically to scan asubstantially rectang-ular raster at a luminescent screen and alsoincluding an auxiliary deflection yoke having horizontal and verticalcoils energizable to modify the effective deflection center of said mainyoke, apparatus for energizing said auxiliary yoke comprising:

a saturable reactor having an alternating current winding and a directcurrent winding;

means connecting said alternating current winding in series between thehorizontal coils of said auxiliary yoke and said horizontal deflectionwave source, whereby to control the energization of said horizontalauxiliary yoke coils and hence the modification of the effectivehorizontal deflection center as a function of the inductive impedance ofsaid alternating current winding and as a function of the horizontaldeflection angle of said beam;

means responsible to temperature changes and connected in series betweensaid direct current reactor winding and a source of direct current tovary the energization of said direct current reactor winding and hencethe inductive impedance of said alternating current reactor winding as afunction of temperature;

means operative at elevated temperatures connecting the vertical coilsof said auxiliary yoke in series between the vertical coils of said mainyoke and said vertical deflection wave source, whereby to vary theenergization of said vertical auxiliary yoke coils in a manner to modifythe effective vertical deflection center in a first sense as a functionof the vertical deflection angle of said beam; and

means including a pair of magnetic contacts located within said directcurrent reactor winding and operative in response to current in saiddirect current winding to effectively short circuit said verticalauxiliary yoke coi-ls at normal temperatures, whereby to vary theenergization of said vertical auxiliary yoke coils in a manner to modifythe effective vertical deflection center in a second sense opposite tosaid first sense as a function of the vertical deflection angle of saidbeam.

4. In a deflection system for a cathode ray picture tube and including amain deflection yoke having horizontal and vertical coils energizablerespectively from horizontal and vertical deflection wave sources todeflect an electron beam horizontally and vertically to scan asubstantially rectangular raster at a luminescent screen and alsoincluding an auxiliary deflection yoke having horizontal and verticalcoils energiza-ble to modify the effective deflection center of saidmain yoke, apparatus for energizing said auxiliary yoke comprising:

a variable reactor having a main winding and a control winding;

the inductive impedance of said main winding being inverselyproportional to the energization of said control winding;

means including a resistor having a negative temperature coefficientconnecting said reactor control winding to a source of direct currentenergy to vary the direct current in said control winding in directproportion to temperature changes;

means connecting said reactor main winding between the horizontal coilsof said auxiliary yoke and said horizontal deflection wave source,whereby to modify the effective horizontal deflection center of saidmain yoke as functions of temperature and of the horizontal deflectionangle of said beam;

means including contacts of a magnetic reed relay mounted within saidreactor control winding to short circuit the vertical coils of saidauxiliary yoke thus enabling inductive energization of said verticalauxiliary yoke coils from said main yoke under normal temperatureconditions, whereby to modify the effective vertical deflection centerin a first sense as a function of the vertical beam deflection angle;and

means including said relay contacts to effectively connect therespective vertical coils of said main and auxiliary yokes in series tosaid vertical deflection wave source, whereby to modify the effectivevertical deflection center of said main yoke under elevated temperatureconditions in a second sense opposite to said first sense as a functionof the vertical deflection angle of said beam.

References Cited UNITED STATES PATENTS 2,834,901 5/1958 Barkow et a13l5--27 X 2,900,564 8/ 1959 Barkow. 3,329,859 7/ 1967 Lem'ke 315-27 XRODNEY D. BENNETT, Primary Examiner.

J. G. BAXT ER, Assistant Examiner.

